2009In September 2009 he received wild card access to the main draw of 2009 BCR Open Romania, where he defeated his fellow countryman Victor Crivoi in the first round, but he lost to Spaniard Rubén Ramírez Hidalgo in the second round.
2010In May 2010, Marius reached his first ATP Challenger Tour final at the Trofeo Paolo Corazzi as a qualifier. On his route to the final he won in three sets against Australian Bernard Tomic in the semifinals but eventually lost the final to German Denis Gremelmayr.
2011The year 2011 started very good for Marius. He reached his second Challenger final at the Tretorn Serie+ event in Kazan, Russia. In the final, he won against 4th seeded German, Andreas Beck, in straight sets.
2012Copil beat World No. 13 Marin Čilić in the first round at the China Open in Beijing.
ATP Challenger Tour finals
Singles: 4 (2–2)